The present invention relates to the fabrication of electronics circuit cards, and more particularly concerns aligning such a card with a connector during assembly thereof.
Many printed circuit cards or boards are attached to long, multicontact connectors to provide an assembly which can be releasably mounted on a larger unit, such as a computer backplane. For this and other applications, a circuit card must be mechanically properly aligned with its connector so as to allow the assembly to fit into the larger unit. For example, card guides in the larger unit are often used to hold card assemblies in place; in midrange computers, card assemblies are mounted into covers or "books" which slide into a cage where the connector engages a bus socket.
The primary alignment criterion for an assembly is the angle between the surfaces of the card holding the electronics components and one or more sides of the connector. If the connector sides are cocked or nonparallel to the card surfaces in a computer card, for example, the pins of the backplane socket will not engage the conductors on the connector as one attempts to lower the card into its guides: the card might not fit at all; some of the connector conductors might not make contact with their mates in the socket; the socket conductors might become bent, making the socket unusable with other cards subsequently pushed into the same slot; or the connector conductors might become bent, rendering the card unusable in other backplane slots.
A conventional solution to the alignment problem is to provide an alignment surface on the connector which fits against one of the surfaces of the card. Clamping the two pieces together while the card conductors are reflow soldered to the connector conductors then assures that the angular alignment between card and connector is proper.
For certain assemblies, however, it is difficult or impossible to use this direct method. For example, circuit cards having surface-mount components on both surfaces must frequently be assembled to straddle-mount connectors having contacts engaging pads on both sides of the card. This type of assembly is used, for example, in personal computers having Microchannel Architecture (tm) backplanes.
This type of assembly could be manufactured in conventional ways with a holding tool for engaging an area of one side of the card and also one side of the connector. However, this would require either very expensive cards and connectors having extremely close thickness tolerances, or laborious manual adjustment of each assembly during manufacture to compensate for thickness variations of individual components.